1. Field of the Invention
The present invention relates to a focus adjustment mechanism for adjusting the focal point at both the short and long focal length extremities when the zoom lens is assembled.
2. Description of the Related Art
At the assembly stage of a zoom lens (zoom lens barrel), the position of a specific lens group (assembly-stage focus-adjusting lens group) relative to another lens group is mechanically adjusted so that the focal point does not change during a zooming operation (i.e., so that the focal point at the long focal length extremity and the focal point at the short focal length extremity are coincident with each other). This adjusting operation is hereinafter referred to as an “assembly-stage focus adjustment operation”.
However, depending on the distribution of optical power, the amount of movement of the assembly-stage focus-adjusting lens group in order to carry out adjustment becomes large in the assembly-stage focus adjustment operation, which sometimes becomes an obstacle to miniaturization of the zoom lens.